NH_4Cl－NH_3·H_2O－H_2O系仲钨酸铵结晶动力学Ⅰ仲钨酸铵蒸发结

用酸碱质子理论解释了ＡＰＴ蒸发结晶酸化过程；讨论了ＮＨ４Ｃｌ掺入对聚合和相变两反应过程的影响机理；研究了一定组分浓度、温度和搅拌条件下，ＡＰＴ结晶诱导期变化的规律；探讨了由诱导期过饱和形成速度控制晶核形成时过饱和度大小的途径。     

NH_4Cl－NH_3·H_2O－H_2O系仲钨酸铵结晶动力学Ⅱ仲钨酸铵蒸发结

用最终产品粒度组成与晶体生长速率结合的方法研究了仲钨酸铵（ＡＰＴ）成核速率。通过图解法和计算，得出了不同溶液组成、加热强度和搅拌转速下ＡＰＴ结晶成核期、最大成核速率出现时间、成核速率最大值、生成晶核总数、最大可能粒径、成核期结束时的固相析出率等特征参数，井探讨了各种条件的影响机理。研究表明：ＮＨ４Ｃ１的掺入使ＡＰＴ成核速率加快、成核期延长；快速搅拌引起ＡＰＴ成核中后期二次晶核大量产生。     

Ag_2S－NH_3－H_2O系热力学

根据银与ＮＨ＿３形成两种银氨络离子Ａｇ（ＮＨ＿３）￣（＋）及Ａｇ（ＮＨ＿３）＿２￣（＋）的特点，应用络离子之间同时平衡的原理，推导了等温电位方程并绘制了Ａｇ＿２Ｓ─Ｈ＿２Ｏ系和Ａｇ＿２Ｓ─ＮＨ＿３─Ｈ＿２Ｏ系的Ｅ─ｐＨ图；在固定电住的前提下又作了后一体系的［Ａｇ￣＋］─ｐＨ图。直观地反映了Ａｇ及Ａｇ＿２Ｓ在有氧存在下能被氦性溶液浸取的可能性及各相存在的热力学稳定区。同时定性表现了Ａｇ＿２Ｓ氨性浸取的热力学条件和操作条件，对ＮＨ＿４Ｃｌ水溶液中氧化浸出Ａｇ＿２Ｓ及复合硫化矿具有指导意义。     

Solubility of sulfur in pure Cr2O3 at 1000°C

Sulfur solubility in pure Cr₂O₃ was measured over a large range of oxygen (10^–6–10^–12 atm) and sulfur (10^–2 -10^–16 atm) partial pressures at 1273 K. Different methods of analysis were used; it was found that the neutronactivation technique produced the most reliable and reproducible results. The results obtained showed that the limiting solubility of sulfur in Cr₂O₃ varied between 16–93 ppm for the range of oxygen and sulfur pressures used in this study. The solubility was found to vary, depending on the combined effect of and . For a given , the amount dissolved increases with an increase of . An empirical equation, was found to best fit the experimental results and indicates a stronger influence of than of . A specific dissolution mechanism connot be formulated from this equation. However, a number of possibilities have been proposed, but none of these specific mechanisms seems to fit the experimental data.     

Solubility of hemimorphite in ammonium sulfate solution at 25 °C

The solubility of natural hemimorphite in ammonium sulfate solution was measured by isothermal solution method at 25 °C and the dissolved residue of hemimorphite was investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) methods. The results show that zinc and silica in hemimorphite simultaneously dissolve in ammonium sulfate solution. The solubility of zinc in solution increases rapidly from 4.5381 mmol/kg in 0.5469 mol/kg ammonium sulfate solution to 11.5083 mmol/kg in 3.7038 mol/kg ammonium sulfate solution. The solubility of silica in solution increases slowly from 2.5509 mmol/kg in 0.5469 mol/kg ammonium sulfate solution to 7.2891 mmol/kg in 3.7038 mol/kg ammonium sulfate solution. The dissolved residue is the characteristic of hemimorphite Zn₄Si₂O₇(OH)₂·H₂O based on the results of the XRD, SEM and FTIR. Thus, no phase transition occurs in the dissolution process of hemimorphite in ammonium sulfate solution.     

Physico-chemistry in distillation process of BiCl3-HCl-H2O system

1　ＩＮＴＲＯＤＵＣＴＩＯＮＣｈｌｏｒｉｎａｔｉｏｎ ｄｒｙｄｉｓｔｉｌｌａｔｉｏｎｍｅｔｈｏｄｉｓａｎｅｆｆｅｃ ｔｉｖｅｗａｙｔｏ ｐｕｒｉｆｙａｎｄｅｘｔｒａｃｔｂｉｓｍｕｔｈｃｏｍｐｏｕｎｄｓｆｒｏｍｔｈｅｃｏｍｐｌｅｘｂｉｓｍｕｔｈｍａｓｓ ,ｂｙｗｈｉｃｈｐｕｒｅｃｈｌｏ ｒｉｎａｔｉｏｎ ｂｉｓｍｕｔｈｐｒｏｄｕｃｔｓａｎｄｈｉｇｈｍｅｔａｌｒｅｃｏｖｅｒｙｒａ ｔｉｏｃａｎｂｅｇａｉｎｅｄ ,ｅｎｖｉｒｏｎｍｅｎｔａｌｐｏｌｌｕｔｉｏｎｂｙｈａｒｍｆｕｌｅｌｅｍｅｎｔｓｃａｎｂｅｐｒｅｖｅ…     

Synthesis of GdF3 from the Gd2O3-NH4HF2 system

GdF3 was synthesized with Gd2O3 and NH4HF2 under atmospheric pressure and vacuum. The effects of pressure,temperature,and reactant ratio on the reaction process were investigated. A new mechanism for the synthesis of GdF3 was proposed. Powdered Gd2O3 started to react with NH4HF2 at low temperature,and the products were GdNH4F4,NH4F,NH3,and H2O. GdNH4F4 decomposed to GdF3 and NH4F after further high-temperature treatment,accompanying the volatilization and decomposition of NH4F. The whole process could be divided into three steps： synthesis,decomposition,and deamination. The initial and final reaction temperatures decreased under vacuum condition. An optimized process for the preparation of GdF3 was obtained： synthesis under atmospheric pressure at low temperature and decomposition and deamination under vacuum at high temperature.     

Hydrothermal conversion of Ti-containing minerals in system of Na_2O–Al_2O_3–SiO_2–CaO–TiO_2–H_2O

Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution.Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na_2O–Al_2O_3–Si O_2–Ca O–Ti O_2–H_2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to Al_4Ti_2 SiO_(12) at low temperatures(60–120 °C), which is similar to anatase in crystal structure. As the temperature continues to rise, Al4Ti2 Si O12decomposes gradually and converts to Ca_3 Ti Si_2(Al_2Si_(0.5)Ti_(0.5)O_(14) at 200 °C. When the temperature reaches 260 °C, Ca Ti O_3 forms as the most stable titanate species for its hexagonal closest packing with O_2-and Ca_2?. The findings enhance the understanding of titanate scaling in the Bayer process and clarify the mechanism of how additive lime improves the digestion of diaspore.     

Primary study of the isothermal phase diagram of the Cu2O-Al2O3-SiO2 ternary system at 1150℃ in air

The isothermal phase diagram of the Cu2O-Al2O3-SiO2 ternary system at 1150℃ was reported for the samples which were prepared from sol-gel method and quenched by water after being heated at 1150℃ for 12 h. Based on the conventional X-ray powder diffraction （XRD） and in situ high-temperature XRD quantitative analysis,in addition to scanning electron microscopy measurement,the phase identification was achieved. Combining the deduction from the component phase diagrams of the binary systems using the phase equilibrium theorem,the primary isothermal phase diagram was plotted over the composition area Cu2O-mullite-SiO2. In this area,the approximate composition areas of two two-phase regions and one three-phase region,（L2＋Cr）,（L2＋M）,and （L1＋L2＋Tr）,were determined. Moreover,the precise composition areas of both of the three-phase regions （L2＋Cr＋M） and （L2＋M＋A） were determined according to the results of conventional and in situ high-temperature XRD quantitative analysis by Rietveld method.     

Dissolving behavior of ammonium paratungstate in (NH4)2CO3–NH3·H2O–H2O system

The effects of temperature, ammonia concentration and ammonium carbonate concentration on the dissolving behavior of ammonium paratungstate were studied in (NH₄)₂CO₃–NH₃·H₂O–H₂O system. The results show that rising temperature, prolonging duration, increasing ammonia concentration and decreasing ammonium carbonate concentration favor dissolving of ammonium paratungstate at temperature below 90 °C, while the WO₃ concentration decreases after a certain time at temperature above 100 °C. Furthermore, the undissolved tungsten exists in the form of either APT·4H₂O below 90 °C or pyrochlore-type tungsten trioxide above 100 °C. In dissolving process, the ammonium paratungstate dissolves into paratungstate ions followed by partially converting to tungstate ion, resulting in the coexistence of the both ions. This study may provide a new idea to exploit a novel technique for manufacturing ammonium paratungstate and pyrochlore-type tungsten trioxide.     

Effect of the magnesium content on the mechanochemical behavior in ternary system Mg–B2O3–C

The influence of Mg content in Mg–B₂O₃–C mixture on the MgO–B₄C composite formation and mechanism of reactions during ball milling process was investigated. In keeping with this aim, a mixture of boron oxide powder along with different amounts of Mg (4–10 mol) and C (1–3 mol) was activated in a ball mill. Thermodynamic calculations and differential thermal analysis (DTA) results revealed that Mg value played a main role, thereby; overall reaction enthalpy and adiabatic temperature (T_ad) changed by variation of magnesium content. T_ad enhanced with the increase in the Mg content and found maximum value (2852 °C) at stoichiometric ratio (Mg = 6 mol). DTA results showed that increasing the activation time to 5.5 h could decrease the temperature of combustion reaction to 530°C before magnesium melting. According to experimental findings, in the mixture of powder with 4 mol Mg, magnesiothermic reaction occurred in MSR mode and no carbothermal reaction took place. However, when the Mg content reached within a range of 9/2–6 mol, the magnesiothermic reaction occurred in MSR mode and activated the carbothermal reaction. Further enhancement in Mg content (10 mol Mg), as a diluent agent, led to MSR magnesiothermic reaction and no carbothermal reduction occurred.     

Novel joining of dissimilar ceramics in the Si3N4–Al2O3 system using polytypoid functional gradients

A unique approach to crack-free joining of heterogeneous ceramics is demonstrated by the use of sialon polytypoids as Functionally graded materials (FGM) as defined by the phase diagram in the system, Si₃N₄–Al₂O₃. Polytypoids in the Al₂O₃–Si₃N₄ system offer a path to compatibility for heterogeneous ceramics. This paper describes successful hot press sintering of multilayered FGMs with 20 layers of thickness 500 μm each. Transmission electron microscopy was used to identify the polytypoids at the interfaces of different areas of the joint. It has been found that the 15R polytypoid was formed in the Al₂O₃-contained layers and the 12H polytypoid was formed in the Si₃N₄-contained layers.     

Synthesis and Structural Determination of Nine-Coordinate K[Gd~Ⅲ(edta)(H_2O)_3]·5H_2O

1 IntroductionMagnetic Resonance Imaging (MRI) ap-peared in l980's. It has gradually become animPortant member in the diagnosis imagingtechnology fieId. Generally, in order to furtherraise the diagnosis quality of MRI, this tech-no1ogy needs to be imPoved and perfectedthrough two respects, i.e., the imProvement ofinstrument design and the aPplication of contra-st agents containing paramagnetic coInPounds.In fact, these paramagnetic comPounds appar-ently shorten relaxation time, increase…     

Crystallization and properties of some CaO-Al2O3-SiO2 system glass-ceramics with Y2O3 addition

The crystallization behavior and mechanical properties of CaO-Al2O3-SiO2 （CAS） system glass-ceramics with addition of Y2O3 were investigated. The optimal sintering temperatures of all heat-treated glasses were altered and the crystallization was accelerated with Y2O3 addition, and only wollastonite as a main crystalline phase was precipitated. The volume fraction of crystalline phase and density were increased with Y2O3 addition. The results suggest that the CAS glass-ceramics would get the lowest sintering temperature and optimal microstructure with the addition of Y2O3 by 3.25 %. The bending strength has a maximum due to the oriented and interlocked wollastonite crystal, which causes crack divert or blunts to limit the further development of the flaw size and increases the surface energy of fracture.     

Equilibrium of hydroxyl complex ions in Pb^2＋-H2O system

The thermodynamics equilibrium principle was used to construct the diagrams for the concentration of complex ions (pc) vs pH, the distribution ratio of lead hydroxyl complex ions (αn) vs pH, and the conditional solubility product of Pb(OH)2 vs pH in the Pb2+-H2O system. The relationship between the equilibrium concentration of each kind of lead hydroxyl complex ions in equilibrium with Pb(OH)2(s) and pH value was shown in the system. The minimum solubility of lead is at the pH value of 10.096-10.997. The distribution ratio of each kind of the lead hydroxyl complex ions is determined as a function of the pH value and the total lead concentration ([Pb]T). The diagram for the conditional solubility product, pKSP vs pH, shows that each kind of lead hydroxyl complex ions existing in the system is dependent upon an optimized pH value at the established concentration of [Pb]T, and that pKSP reaches the minimum at the pH value of 10.3-11.2. The results can provide a theoretical basis for removing lead ions from wastewater by the neutralization and hydrolyzation technology.     

Synthesis and Structural Determination of Nine-coordinate K_2[Y~Ⅲ(dtpa)(H_2O)]·7H_2O

1 ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｃｏｍｐｏｕｎｄｓｏｆｔｈｅｒａｄｉｏａｃｔｉｖｅｅｌｅ ｍｅｎｔ90 Ｙｈａｖｅｏｆｔｅｎｂｅｅｎｕｓｅｄｆｏｒｔｈｅｔｒｅａｔ ｍｅｎｔｏｆｅｖｅｒｙｋｉｎｄｏｆｃａｎｃｅｒ[1]ｂｅｃａｕｓｅｔｈｅｙｃａｎｅｍｉｔｐｕｒｅａｎｄｈｉｇｈ ｅｎｅｒｇｙ β ｒａｙａｎｄｐｏｓｓｅｓｓｔｈｅａｐｐｒｏｐｒｉａｔｅｈａｌｆ ｌｉｆｅ (ｔ1/ 2 =64 0ｈ)ａｎｄｍｏｄｅｒａｔｅｅｎｅｒｇｙ(Ｅｍａｘ=2 .2 7ＭｅＶ) .Ｈｏｗｅｖｅｒ,ｔｈｅｒａｄｉｏａｃｔｉｖｅｒａｙｓｏｆｔｈｅ90 Ｙｉ…     

Experimental phase diagram determination and thermodynamic assessment of the Gd2O3–CoO system

New phase diagram data and a thermodynamic assessment of the Gd₂O₃–CoO system using the CALPHAD approach are presented, giving liquidus data and mutual solid solubilities of Co in Gd₂O₃ and Gd in CoO. The thermodynamic model parameters for the ternary Gd–Co–perovskite phase and for the mutual solid solubilities of Co in Gd₂O₃ and Gd in CoO are optimized to reproduce these new experimental data, as well as phase diagram data from literature. The Gd₂O₃–CoO phase diagram is refined based on the results of experiments using combined differential thermal analysis and thermogravimetry, scanning electron microscopy and X-ray diffraction techniques.     

Decomposition mechanisms and non-isothermal kinetics of LiHC_2O_4·H_2O

The thermal decomposition process of LiHC2O4·H2O from 30 to 600 ℃ was investigated by the thermogravimetric and differential scanning calorimetry (TG-DSC). The phases decomposited at different temperature were characterized by X-ray diffraction (XRD), which indicated the decompositions at 150, 170, and 420℃, relating to LiHC2O4, Li2C2O4, Li2C2O4, and Li2CO3, respectively. Reaction mechanisms in the whole sintering process were determined, and the model fitting kinetic approaches were applied to data for non...